Apparatus for generating gas by electrolysis of a liquid

ABSTRACT

Apparatus for generating gas by electrolysis of a liquid comprises an electrolysis cell and a housing for the liquid. The housing comprises a first chamber for storing the liquid for supply to the electrolysis cell, the first chamber having an inlet for replenishing the liquid, and an outlet through which liquid is supplied from the first chamber to the electrolysis cell, and a second chamber for containing liquid which is a product of the electrolysis reaction and which is enriched with a first gaseous product of the electrolysis reaction, the second chamber having a gas outlet for controlled release of the first gaseous product. A first channel in the housing connects the first and second chambers. The channel provides a trap for liquid which can provide a barrier to passage of gas between the first and second chambers, irrespective of the level to which liquid in the first chamber falls during normal operation.

The present invention relates to apparatus for generating gas byelectrolysis of a liquid.

U.S. Pat. No. 5,037,518 discloses apparatus for generating hydrogen byelectrolysis of water. The apparatus comprises an electrolysis cell.Water is supplied to the cell from first and second reservoirs. Hydrogenwhich is discharged from the cell contains water, for example asdroplets or as vapour. The hydrogen is separated from associated waterin a chamber in which bulk water can collect. The hydrogen is dischargedfrom the chamber and passes through dryer components which include adrying coil and a desiccant chamber, before discharge to an end useapplication.

Water from the electrolysis cell is discharged into an annex to thefirst reservoir which has a vent for associated oxygen. Accumulation ofoxygen in the first reservoir itself is minimised in this way.

Similarly, water from the separation chamber is discharged into an annexto the second reservoir which has a vent for associated hydrogen.Accumulation of hydrogen in the second reservoir itself is minimised inthis way.

The use of first and second reservoirs, with associated annexes,complicates the assembly of the apparatus disclosed in U.S. Pat. No.5,037,518.

The present invention provides apparatus for generating gas byelectrolysis of a liquid, which includes a housing comprising a firstreservoir chamber, a second chamber for separation of liquid andassociated reaction product gas, and an interconnecting channel.

Accordingly, in one aspect, the invention provides apparatus forgenerating gas by electrolysis of a liquid, comprising:

-   -   a. an electrolysis cell;    -   b. a housing for liquid with an inlet through which liquid in        the housing can be replenished, which comprises:        -   i. a first chamber for storing the liquid for supply to the            electrolysis cell, having an outlet through which liquid can            be supplied from the first chamber to the electrolysis cell,        -   ii. a second chamber for containing liquid which is a            product of the electrolysis reaction and which is enriched            with a first gaseous product of the electrolysis reaction,            the second chamber having a gas outlet for controlled            release of the first gaseous product, and        -   iii. a channel in the housing which connects the first and            second chambers, in which the channel provides a trap for            liquid which can provide a barrier to passage of gas between            the first and second chambers, irrespective of the level to            which liquid in the first chamber falls during normal            operation.

The apparatus of the invention has the advantage that the housing can beprovided simply and efficiently as a single component, which providesfirst and second chambers and the interconnecting channel. As a singlecomponent, the housing, comprising the first and second chambers and thefirst channel, can be manipulated in such a way that the parts thereofare fixed relative to one another. The materials of parts (first andsecond chambers and first channel) of a housing which is provided as asingle component can be common. A housing which is provided as a singlecomponent can be formed from separate parts, which can be assembledtogether. The parts can be fitted together by bonding (for example bywelding or using a separate bonding material), or relying on mechanicalinterconnection. One or more parts of the housing can be formed bymoulding when they are formed from polymeric material. Preferably, thehousing is formed as a single part by a process such as moulding.Formation of the housing as a single part simplifies assembly, forexample removing the need to form seals between the first and secondchambers and an interconnecting channel.

Preferably, the inlet for replenishing the liquid in the housing isprovided in the first chamber.

The trap in the channel will generally be U-shaped, in which a wallextends downwardly into the channel, and defines the arms of the “U”.The bottom wall of the “U” can be rounded so that it follows the sidewalls. The channel can be open laterally at its base so that it extendsinto an adjacent chamber; for example the channel can itself be providedby an elongate chamber which extends laterally, with one or more wallsextending into the elongate chamber to define one or more generallyU-shaped traps.

The channel can provide a barrier to passage of gas by ensuring that thetrap remains full of liquid at the bottom of the downwardly extendingwall so that the liquid level overlaps the wall. This can preventmigration of gas between the second and first chambers (other than insolution).

Ensuring that the trap remains full of liquid at the base of the “U”, sothat it overlaps the bottom of the wall, can be achieved by providing astep between the first and second chambers, in which the bottom of thewall which defines the “U” is lower than the step. This means that theliquid level in the first chamber can drop below the level of the step,while the liquid level in the second chamber remains at or close to thelevel of the step.

Ensuring that the trap remains full of liquid at the base of the “U”, sothat it overlaps the bottom of the wall, can be achieved by ensuringthat the bottom of the wall which defines the “U” is located below thelowest level to which liquid in the first chamber falls during normaloperation of the apparatus, for example below a predetermined minimumlevel for the liquid which is defined by a level control mechanism.

The thickness of the downwardly extending wall (which effectivelydefines the distance between the arms of the “U”) will not generally becritical to the functioning of the apparatus.

The housing can be formed as a single piece. Alternatively, it can beformed from two or more pieces are then assembled to form the housing,for example using a bonding technique which does not use an additionalmaterial (especially welding), or using a bonding technique which usesan additional material such as an adhesive, or by soldering or brazing,or mechanically. The technique for forming the housing will depend onthe material(s) from which it is made. Preferably, at least part of thehousing is formed from a polymeric material. For example, the walls ofthe first chamber, or the walls of the second chamber, or both, can beformed from a polymeric material. Preferably, the walls of the first andsecond chambers are formed from the same material, especially apolymeric material.

When one or more parts, or all, of the housing is formed from apolymeric material, they are preferably formed by moulding. Examples ofsuitable moulding techniques include blow moulding, injection moulding,rotational moulding and vacuum forming. Preferably, the first and secondchambers are formed together in a moulding operation, especially arotational moulding operation.

Suitable polymers which can be used in the housing include polyolefins,especially polyethylene and polypropylene, polyamides, polyesters,polycarbonates etc. The polymer should be selected for appropriatephysical properties (for example, melting or softening temperature,tensile properties etc) which will enable it to withstand the conditionsto which it will be exposed during use, and also ease of manufacture.

A polymeric housing can include reinforcement elements to help it towithstand pressures imposed by gas which accumulates within it. Forexample, a polymeric housing can have tie rods moulded within it,extending between opposite walls, especially between opposite top andbottom walls.

When the housing is formed from a transparent material, or especially atranslucent material, a visible signal can be provided by means ofpowered light source which is attached to the housing, especially theoutside of the housing. When a power signal is supplied to the lightsource, the housing or liquid within it or both can then be illuminatedto provide a visible signal, for example that the liquid level withinthe housing has exceeded a predetermined maximum (or intermediate)level, or has dropped below a predetermined minimum (or intermediate)level, or that there are impurities in the liquid in the housing (forexample as determined using a conductivity sensor or other measuringdevice), or that a component within the apparatus is not functioning asintended. It an be preferred for the light source to comprise one ormore light emitting diodes. The light source can include elements whichshow different colours when powered. The light source can be arranged toflash to indicate a condition of the apparatus.

The apparatus of the invention includes an electrolysis cell in whichthe liquid can be exposed to a potential difference between an anode anda cathode, so that the liquid is oxidised at the anode and is reduced atthe cathode. For example, when the liquid is water, oxygen is generatedat the anode and hydrogen is generated at the cathode. Known cells forelectrolysis of water make use of a solid polymeric ion-exchangemembrane for the electrolyte, for example based on a thin layer of anion exchange membrane. A suitable ion exchange material is a sulphonatedperfluorocarbon membrane such as that sold under the trade mark NAFION.Suitable electrodes can be based on catalytic systems, for example basedon a mixture of platinum and iridium together with a platinised titaniumscreen. The construction of a suitable electrolysis cell is discussed inrelation to FIG. 2 of U.S. Pat. No. 5,037,518.

It can be preferred in order to minimise the risk of damage to theelectrolysis cell to control the purity of the liquid that is suppliedto the cell. The apparatus can include a detector for impurities in theliquid. The detector can detect impurities in liquid in the firstchamber. The detector can detect impurities in the liquid which are inthe line extending from the first chamber to the electrolysis cell. Thedetector can measure a property of the liquid which is affected by thepresence of impurities. Relevant properties might include, for example,conductivity, optical transmission characteristics (clarity, change incolour etc), etc. When the liquid is water, it will be preferred todetect impurities by measuring conductivity. Preferably, the supply ofpower to the cell is interrupted in the event that impurities aredetected.

Preferably, the housing includes:

-   -   i. a third chamber for containing liquid which is a product of        the electrolysis reaction and which is enriched with a second        gaseous product of the electrolysis reaction, the third chamber        having a gas outlet for controlled release of the third gaseous        product, and    -   ii. a second channel in the housing which connects the third        chamber to at least one of the first and second chambers, in        which the channel provides a trap for liquid which can provide a        barrier to passage of gas, irrespective of the level to which        liquid in the first chamber is discharged during operation.

The advantage identified above of forming first and second chambers as asingle component is enhanced when the housing includes a third chamber,and a second channel which connects the third chamber to at least one ofthe first and second chambers.

Preferably, the second channel connects the third chamber to the secondchamber. This has the advantage that, if the gas outlet in the thirdchamber ceases to function adequately (for example because it becomesblocked), an increase in the pressure of the second gaseous product inthe third chamber results in displacement of liquid in the secondchannel so that the second gaseous product is discharged into the secondchamber. The combination of the first gaseous product in the secondchamber and the second gaseous product which is discharged into thesecond chamber from the third chamber might be explosive (for example inthe case of hydrogen and oxygen in apparatus which is used for theelectrolysis of water). However, it is an advantage that this mixture iscontained within the second chamber rather than the first chamberbecause the second chamber will generally have a smaller volume than thefirst chamber, so that the volume of the gas mixture will be smaller inthe second chamber than would be the case in the first chamber.Accordingly, the series arrangement of the third, second and firstchambers can help to minimise the adverse effects of an explosion in theevent that a gas outlet fails to function adequately.

Preferably, the apparatus includes a level control mechanism to enablecontrol over the level of liquid in the reservoir, in particular whichprevents the level falling below a predetermined minimum level duringoperation of the apparatus. The level control mechanism will generallyinclude a level detector; preferably, the level detector initiates aresponse in the event that the liquid reaches a predetermined level,which might be a maximum level, or a minimum level, or an intermediatelevel. The level detector can function mechanically, for example using afloat. Movement of the float can cause an electrical switch to movebetween open and closed positions. The level detector can measurechanges in conductivity according to whether the detector is immersed inthe liquid, or according to a change in the depth to which the detectoris immersed. It is preferred to use one or more level detectors whichmeasure the conductivity of the liquid, especially when the liquid iswater. The level detector can measure changes in the optical propertiesof fluid (liquid or gas) which are present in the first chamber: inparticular, a signal can be generated because of the different opticalcharacteristics of the liquid and air.

Preferably, the level control mechanism generates a signal when thelevel of the liquid in the first chamber exceeds a predetermined maximumlevel. The signal can be a warning signal, especially a visible signalor an audible signal or both, when the first chamber is filled manually.The signal can cause automatic supply apparatus to shut off the supply,when this is used to replenish the first chamber. The apparatus caninclude a level control mechanism which measures the level of liquid inthe first chamber continuously, for example to be displayed on adisplay.

Preferably, the level control mechanism generates a signal when thelevel of the liquid in the first chamber is less than a predeterminedminimum level. Generally, the supply of power to the cell will beinterrupted in the event that the level of liquid is less than apredetermined minimum level. The level control mechanism can generate asignal when the level of liquid in the first chamber is above thepredetermined minimum level. That signal can be a warning signal,especially a visible signal or an audible signal or both.

Preferably, the detector for the minimum level of liquid in the housingis provided in the second chamber. In order for the detector to be ableto generate a signal when the level of liquid in the first chamber isless than a predetermined minimum level, it will then be above the levelof any ridge which separates the first and second chambers. An advantageof locating the minimum level detector in the second chamber is that itis able to generate a signal when the level in the second chamber dropsbelow the predetermined minimum level even when the level in the firstchamber has not also dropped. For example, this can occur when the ventfor gas from the second chamber is blocked, or in the event of anexplosion condition in the second chamber.

Preferably, the inlet for replenishing the liquid in the first chamberhas a central funnel part which extends downwardly into the firstchamber to a point which is lower than the said predetermined minimumlevel of liquid in the first chamber. This has the advantage that aclosure cap (for example, a cap which can engage the inlet by means ofcooperating threads) on the inlet is not in direct contact with gas thatis present in the first chamber between the liquid in the chamber andthe upper surface of the chamber. This means that, in the event that amalfunction leads to the presence of an explosive gas in the firstchamber, the closure cap on the inlet will not be exposed to the forceof the explosion.

Preferably, the second chamber has an inlet for the liquid andassociated gaseous product which is located above the predeterminedminimum level of liquid in the first chamber, preferably around the meanlevel of the liquid in the first chamber during normal operation of theapparatus. This can facilitate separation of the liquid and associatedgaseous product, and can minimise re-association of the liquid and thegaseous product. Preferably, the third chamber (when present) has asimilar inlet.

Generally, the second chamber will extend above the maximum level towhich the first chamber is normally filled with liquid, and the gasoutlet will be provided above this maximum level. The portion of thesecond chamber which is above this maximum level can ensure that gas canbe retained within the second chamber even when the level of liquid inthe first chamber is at its maximum. Positioning the gas outlet abovethe said maximum level means that liquid will not be discharged throughthe gas outlet even when the level of liquid in the first chamber is atits maximum. It also means that a filter in the gas outlet (whenpresent) will not get wet.

Preferably, the housing includes at least one other outlet for liquidwhich collects in the housing in a region thereof which is lower thanthe outlet through which liquid is supplied from the first chamber tothe electrolysis cell.

Preferably, a portion of the wall of the housing which defines the firstchamber is defined by a line of weakness so that the wall fails at theline of weakness when the pressure in the first chamber reaches anexcessively high level. For example, a groove can be cut in the wall ofthe housing extending partway through its thickness. The groove can begenerally rounded, especially circular so that, in the event of thepressure reaching a high level, especially if an explosive force isgenerated, a round portion of the wall of the first chamber breaks of,allowing release of pressure. The provision of a line of weakness hasthe advantage of providing control over how the first chamber will failin the event that high pressure levels are obtained in the chamber. Forexample, the portion of the wall of the first chamber at which it failscan be arranged in a location within the apparatus such that externaladverse effects are minimised. For example, the failure portion can beforced towards the interior of the apparatus so as not to cause injuryto a nearby operator.

Preferably, the second chamber (and the third chamber, if present)includes a filter in its gas outlet to minimise ingress of contaminantmaterial into the said chamber. The filter should prevent ingress ofparticulate contaminants, and also contaminants in liquid or vapourform, especially organic solvent vapours. Examples of suitable filterscan be based on activated alumina and activated carbon, possiblyimpregnated with other components such as potassium permanganate, forexample as sold by Jones & Attwood Limited under the trade marksJABLEND, JASORB and JACARB.

Preferably, the first chamber includes an outlet for controlled releaseof gas. Preferably, the gas outlet in the first chamber has a filter init to minimise ingress of contaminant material into the said chamber.The filter can have generally the same functional characteristics as thefilter discussed above for use in the second chamber.

Preferably, the ratio of the volume of the first chamber to the volumeof the second chamber is at least about 20, more preferably at leastabout 30, especially at least about 40.

Preferably, the ratio of the volume of the first chamber to the volumeof the third chamber is at least about 20, more preferably at leastabout 30, especially at least about 40.

Preferably, the ratio of the volume of the second chamber to the volumeof the third chamber is not more than about 2, more preferably not morethan about 1.5. Preferably, the value of the said ratio is at leastabout 0.5, more preferably at least about 1.5.

Preferably, the apparatus includes a separator device for separating thegas which is to be generated from the liquid.

Preferably, the separator device includes a separator chamber having aliquid outlet through which liquid is discharged to the second chamber,and a gas outlet, the gas outlet having a valve which closes when theliquid level in the separator chamber exceeds a predetermined level. Theseparator device can include a quantity of an adsorbent, especially adesiccant when the liquid to be adsorbed is water. Examples of suitabledesiccants include alumina, silica and the like.

Preferably, the housing includes formations for fixing the separatordevice to the housing. For example, the separator device can be fastenedto the housing mechanically by means of threaded fasteners. The housingcan be provided with threaded bores to engage machine screws. When thehousing is formed from a polymeric material, it can include threadedinserts which can engage the fasteners.

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation in the form of a flow chart,showing components of gas generation apparatus.

FIG. 2 is an isometric view from the front of the bottom of the housingof the apparatus shown in FIG. 1.

FIG. 3 is an isometric view from the back of the top of the housing ofthe apparatus shown in FIG. 1.

FIG. 4 is a view of the back of the housing, partially in section.

FIG. 5 is an isometric view of separator apparatus which can be fittedto the housing, to separate a gaseous reaction product from liquid whichis carried with it.

Referring to the drawings, FIG. 1 shows gas generation apparatus such ashydrogen generation apparatus in which water is exposed to a potentialdifference in an electrolysis cell. The discussion that follows will berestricted to this application, although the apparatus of the inventioncan be used with other liquids to generate other gases.

The gas generation apparatus comprises a reservoir 2 for the water whichis to be treated. Water is discharged from the reservoir 2 through anoutlet 4. The outlet has a conductivity sensor 6 mounted in it by whichthe presence of impurities in water from the reservoir can be detected.In the event that impurities are detected, by an increase inconductivity above a predetermined level, the power supply to theelectrolysis cell can be interrupted.

Water from the reservoir is pumped by means of a pump 8 through anelectrolysis cell 10 which contains an anode, a cathode and a solidpolymeric electrolyte which is provided by an ion-exchange membrane,especially a sulphonated perfluorocarbon membrane such as that soldunder the trade mark NAFION. Details of the construction of anelectrolysis cell such as might be used in the apparatus of the presentinvention are disclosed in U.S. Pat. No. 3,870,616 and U.S. Pat. No.5,037,518.

Water from the anode side of the electrolytic cell is pumped from theelectrolytic cell to a first reservoir separator chamber 12 in whichoxygen which is associated with the water (carried by the water insolution or as dispersed bubbles) can separate from the water.

Hydrogen is discharged from the cathode side of the electrolysis cellinto separator apparatus 20 through a line 22. The hydrogen that issupplied to the separator apparatus has water associated with it, asdroplets or as vapour. The separator apparatus includes a manifold block201 which is attached a separator chamber 24 and an adsorption chamber28. The manifold block includes a first mounting point 202 at which theseparator chamber 24 can be physically connected to the block,preferably by means of a screw or bayonet type fitting. The manifoldblock includes a second mounting point 203 at which the adsorptionchamber 28 can be physically connected to the block.

The manifold block 201 has a plurality of conduits disposed internallyand externally. The conduits enable fluid communication between theseparator chamber 24 and the adsorption chamber 28. The mixture ofhydrogen and water is conducted through line 22 to a manifold inlet 204which is connected to an inlet 206 located at the top of the separatorchamber by means of an inlet conduit 31 within the manifold block 23.Line 22 can have a pressure switch 207 in it which closes the line whenthe pressure in it exceeds a predetermined level, for example in theevent that the pressure in the chamber 24 increases because the wateroutlet line is blocked and water accumulates in the chamber, closing thefloat valve 27. The pressure switch may be attached to the manifoldblock, disposed at the manifold inlet 204.

The hydrogen/water mixture enters the top of the separator chamber 24through the inlet 206 and liquid water collects at its base. Hydrogencan escape from the chamber 24 through an outlet 208 located at the topof the chamber. The discharge of hydrogen from the chamber is controlledby means of a float valve 27. The float valve is sensitive to the levelof water in the chamber. The float valve closes the hydrogen outlet 208from the chamber when the level of water reaches a predetermined level,to prevent collected water passing from the chamber into othercomponents of the separator apparatus, for example in the event thatwater cannot be discharged from the chamber.

After passing through the separator outlet 208, the hydrogen passesthrough a connecting conduit 209 within the manifold block to aconnector outlet 210, through which the hydrogen flows into an externalconduit 212 disposed outside the manifold block. The external conduit isprovided by a drying membrane material, preferably a moisture exchangedrying membrane (for example a membrane made from a sulphonatedperfluorocarbon membrane such as that sold under the trade mark NAFION).The use of a drying membrane of this general kind is disclosed in U.S.Pat. No. 5,037,518.

Hydrogen which has passed through the external conduit is supplied to aconnector inlet 213 in the manifold, through which the hydrogen flowsinto the connecting conduit 209 within the manifold block. A pressuresensor 214 can be included between the external conduit and theconnecting conduit 209 in the manifold block so as to detect undesirableincreases in the pressure. It can also detect unwanted reductions inthat pressure which can indicate a leak in the line through whichhydrogen is supplied to the end use application.

The pressure sensor can be disposed in the external conduit or at theconnector inlet. Preferably, the pressure sensor is attached to themanifold block.

The hydrogen in the connecting conduit then passes into an adsorptionchamber 28 through an inlet 216, the adsorption chamber being physicallyconnected to the manifold block at the second mounting point 203.Preferably, the hydrogen is conducted in a line 215 within theadsorption chamber before being released into the adsorption chamber atthe top. The adsorption chamber preferably contains a desiccant such assilica gel or a molecular sieve or both. The adsorption chamber 28 hasan outlet 217 located near the bottom of the chamber through which thedried hydrogen is released into a conduit 218 within the manifold block.By locating the inlet 216 and outlet 217 at opposite ends of theadsorption chamber, the hydrogen has to pass through the majority of thelength of the adsorption chamber, and therefore its exposure to theadsorbent is maximised. The relative positions of the inlet 216 andoutlet 217 may be reversed.

The conduit 218 is connected at an outlet 219 to a line 220 throughwhich the hydrogen passes to an outlet 222 that is adapted forconnection to an end use appliance. The line 220 can include a valve,preferably a solenoid valve 221, which can close the outlet 222 when theapparatus is not in use, or when the pressure in the line is either toohigh or too low (perhaps due to a leak).

Water which collects in the separator chamber 24 is supplied through aline 30 to a second reservoir separator chamber 32 in which hydrogenwhich is associated with the water (carried by the water in solution oras dispersed bubbles) can separate from the water.

FIGS. 2, 3 and 4 show a housing 100 which incorporates the reservoir 2and the first and second reservoir separator chambers 12, 32. Inrelation to the discussion of the housing shown in FIGS. 2 and 3, thereservoir will be referred to as the first chamber, and the first andsecond reservoir separator chambers will be referred to as second andthird chambers, respectively. The housing is formed as a single mouldingfrom a polyolefin such as polyethylene or polypropylene. A preferredtechnique for forming the housing involves rotational moulding.

The housing has an inlet 102 for water to be supplied to the firstchamber 2. The first chamber is connected to the second and thirdchambers 12, 32 by means of first and second channels 104, 106. Thechannels can be considered as sections an elongate chamber 108 whichextends along the back of the housing, at a level below the base of thefirst chamber 2.

The second and third chambers 12, 32 are substantially identical inshape and configuration. Each of them communicates with the elongatechamber 108 (see especially FIGS. 2 and 4), and has an enlarged headportion 110 which has in it a gas outlet. The chambers are separated bywalls 111 which extend downwardly into the chamber. The walls eachdefine a U-shaped trap. When the elongate chamber is filled with waterto a depth which covers at least the bottom of each of the walls, thewall and the water in the elongate chamber provide a gas impermeablebarrier between adjacent chambers. During normal operation of theapparatus of the invention, water will remain in the elongate chamber tosufficient depth to ensure that it covers at least the bottom of each ofthe walls because the bottom of each of the walls 111 is below theminimum depth to which the water in the first chamber drops, and becauseof the step between the water outlet 4 and the second and third chambers12, 32 which is higher than the bottom of each of the walls.

As shown in FIG. 3, each of the gas outlets has a vent component 112mounted in it, to which can be fitted a removable filter cartridge 113.The filter cartridges prevent ingress of contaminants into the housing.Suitable filter materials include activated carbon materials, activatedalumina materials, activated silica materials etc. The enlarged headportion 110 of each of the second and third chambers has an inlet 114for water which has gas associated with it. The water which is admittedto the second chamber 12 has hydrogen associated with it, and the waterwhich is admitted to the third chamber 32 has oxygen associated with it.The water inlets 114 are located at about the mean level of water in thefirst chamber during normal operation of the apparatus.

The housing has openings 116 formed in its back wall and in a wall ofthe third chamber to receive level sensors for liquid within it. One ofthe sensors is positioned to detect when the liquid level reaches apredetermined maximum level, and the other of the sensors is positionedto detect when the liquid level reaches a predetermined minimum level.Preferably, the minimum level sensor is provided in the second chamberor the third chamber, so that it can detect a reduction of the level ofliquid in that chamber which is due to, for example a blocked gas outputvent or an explosion condition in that chamber, in addition to areduction in the level of water in the first chamber. Intermediatesensors can be provided to measure when liquid levels reach intermediatelevels, for example to provide a warning that a maximum level or aminimum level is soon to be exceeded. An array 118 of light emittingdiodes can be provided in a recess 120 in the base of the housing, whichcan illuminate the housing according to the signals provided to it bysensors, including level sensors, sensors as to the purity or othercondition of the liquid etc. The translucence of the material of thehousing arising from the use of a polymer such as a polyolefin canencourage the illumination of the housing in this way making the warningsignal provided by the diodes readily visible. The signal which isgenerated when the water reaches the minimum water level causes thesupply of power to the electrolysis cell to be interrupted to avoid thecell running with inadequate water: this can damage the cell. A recess121 in the housing, defined by an inclined face 122, towards the frontof the housing, can facilitate visual inspection of the water level. Itcan be provided with markings to help with this.

The first chamber 2 is generally flat in the sense that its depth issmaller than its width and its length. However, it has a protrudingcircular protrusion located below the inlet 102, which has a dischargeoutlet opening 4 in it through which water can be discharged to theconductivity sensor 6, for supply to the conductivity cell. The inlet102 includes an inlet tube which extends into the first chamber to alevel which is lower than the lowest level to which the water will dropduring normal operation of the apparatus. The inlet tube can be closedby a cap 124. The inlet tube can contain a filter 126 to minimise therisk of particulate and ionic impurities (which might damage theelectrolysis cell) being introduced into the first chamber. It can beparticularly preferred for a filter in the inlet tube to reduce theionic content in the water in order to reduce ionic conductivity.

The housing has a circular groove 127 cut into its lower face to definea circular area of the wall. The groove represents a line of weakness atwhich the housing can open in the event of excessive pressure within it,especially in the event of an explosion within the housing.

The housing has a number of additional outlet mouldings 128 provided onits lower face. Preferably, the housing is moulded with each of theoutlet mouldings closed, so that those outlet mouldings which need to beused to drain liquid from the housing which is retained when the housingis emptied through the discharge outlet opening 4 can be opened byremoving the tip by cutting (including drilling). This appliesparticularly the outlet moulding 130 on the elongate chamber 108 whichprovides the first and second channels extending between the chambers 2,12, 32. One of the outlet mouldings 132 can be used to locate the array118 of light emitting diodes which is used to provide visible warningsignals, which can be retained on the outlet moulding mechanically, forexample by means of a circlip.

The housing has a number of tie rods 134 moulded within it extendingbetween the opposite top and bottom walls of the first chamber 2. Thesecan enhance the ability of the housing to withstand internal pressure.

The housing has a plurality of internally threaded nuts 136 moulded intoits lower face in an array around the recess 121. These can receivethreaded machine screws to fix apparatus for separating hydrogen gasfrom associated water carried with the gas as droplets or as vapour.

Separator apparatus 200 is shown in FIG. 4, which comprises a manifoldblock 201 with the separator chamber 24 and the adsorption chamber 28physically connected to it. In the particular embodiment shown theseparator chamber is located below the manifold block, and theadsorption chamber is located above the manifold block. The separatorapparatus includes pressure sensors 207 and 214, a solenoid valve 221,inlets 204 and 213, and outlets 210 and 222. The manifold block can havebores extending through it, in the peripheral region outside theseparator and adsorption chambers, for receiving fasteners such asmachine screws whose ends can be received in the nuts in the bottom faceof the housing 100. Separator apparatus with such features is disclosedin an application which is filed with the present application whichclaims priority from UK patent application no. 0305007.7. Subject matterdisclosed in the specification of that application is incorporated inthis specification by this reference.

When the apparatus of the invention is in use, water is maintained at alevel in the housing between the maximum and minimum levels provided inthe openings 116 in the back wall. If the water level falls between theminimum level, Water is supplied from the first chamber 2 of the housing100 through the outlet 122 to the conductivity sensor 6.

Water is fed from the anode side of the electrolytic cell to the thirdchamber 32. The water has oxygen associated with it (in solution or asdispersed bubbles) which can separate from the water in the thirdchamber. Oxygen which separates from the water can vent to atmospherethrough the vent component 112 mounted in it and the filter cartridge113.

Water is fed from the separator apparatus 20 to the second chamber 12.The water has hydrogen associated with it (in solution or as dispersedbubbles) which can separate from the water in the second chamber.Hydrogen which separates from the water can vent to atmosphere throughthe vent component 112 mounted in it and the filter cartridge 113.

Water is maintained in the elongate chamber 118 to a depth such that thebottom of each of the walls 111 is immersed in the water. This ensuresthat gas is not able to pass between adjacent chambers through theelongate chamber, at least during normal operation of the apparatus.Accordingly, hydrogen and oxygen are maintained separately in theenlarged head portions of the second and third chambers, from where theycan vent to atmosphere.

In the event of failure of one of the vents (in particular if it were tobecome blocked so that pressure in the respective chamber increases), orin the event of an explosion condition in a chamber, water in the trapcan be displaced so that the gas flows into the next adjacent chamber.This can be detected by a minimum water level detector in the chamber inquestion, and can lead to the interruption of power to the electrolysiscell. If the failure is in the third chamber 32, oxygen will flow intothe second chamber 12 in which hydrogen has collected. The potentiallyexplosive mixture is contained within a space which is smaller than thecorresponding space in the first chamber so that, in the event of anexplosion, the quantity of the explosive gas mixture is small. If thefailure is in the second chamber 32, hydrogen will flow into the firstchamber and possibly also into the third chamber 12. The volume of thethird chamber is the same as that of the second chamber. In the absenceof hydrogen in the first chamber, the risk of explosion as a result ofan increase in the oxygen concentration of the collected gas is small.

If failures occur in both the second and the third chambers, oxygen andhydrogen can collect in the first chamber. Gas can vent from the firstchamber through the vent and filter. In the event of an explosion in thefirst chamber, the bottom wall of the first chamber fails by blowing outthe circular region defined by the groove 127.

1-19. (canceled)
 20. Apparatus for generating gas by electrolysis of aliquid, comprising: an electrolysis cell; a housing for liquid with aninlet through which liquid in the housing can be replenished, thehousing being provided as a single component, which comprises: i. afirst chamber for storing the liquid for supply to the electrolysiscell, having an outlet through which liquid can be supplied from thefirst chamber to the electrolysis cell, ii. a second chamber forcontaining liquid which is a product of the electrolysis reaction andwhich is enriched with a first gaseous product of the electrolysisreaction, the second chamber having a gas outlet for controlled releaseof the first gaseous product, and iii. a first channel in the housingwhich connects the first and second chambers, in which the said channelprovides a trap for liquid which can provide a barrier to passage of gasbetween the first and second chambers, irrespective of the level towhich liquid in the first chamber falls during normal operation, inwhich the first chamber, the second chamber and the first channel arefixed relative to one another to allow the housing to be manipulatedwithin the apparatus as a single component.
 21. Apparatus as claimed inclaim 20, in which the second chamber includes a filter in its gasoutlet to minimize ingress of contaminant material into the secondchamber.
 22. Apparatus as claimed in claim 20, in which the inlet forreplenishing the liquid in the housing is provided in the first chamber.23. Apparatus as claimed in claim 20, in which the housing includes: i.a third chamber for containing liquid which is a product of theelectrolysis reaction and which is enriched with a second gaseousproduct of the electrolysis reaction, the third chamber having a gasoutlet for controlled release of the third gaseous product, and ii. asecond channel in the housing which connects the third chamber to atlast one of the first and second chambers, in which the channel providesa trap for liquid which can provide a barrier to passage of gas,irrespective of the level to which liquid in the first chamber isdischarged during operation.
 24. Apparatus as claimed in claim 22, inwhich the second channel connects the third chamber to the secondchamber.
 25. Apparatus as claimed in claim 22, in which the thirdchamber includes a filter in its gas outlet to minimize ingress ofcontaminant material into the third chamber.
 26. Apparatus as claimed inclaim 20, in which the first chamber includes an outlet for controlledrelease of gas.
 27. Apparatus as claimed in claim 20, which includes alevel control mechanism which prevents the level of liquid in thereservoir falling below a predetermined minimum level during operationof the apparatus.
 28. Apparatus as claimed in claim 26, in which thelevel control mechanism includes a minimum liquid level detector that islocated in the second chamber.
 29. Apparatus as claimed in claim 26, inwhich the inlet for replenishing the liquid in the first chamber has acentral funnel part which extends downwardly into the first chamber to apoint which is lower than the said predetermined minimum level of liquidin the first chamber.
 30. Apparatus as claimed in claim 26, in which thehousing includes at least one other outlet for liquid which collects inthe housing in a region thereof which is lower than the outlet throughwhich liquid is supplied from the first chamber to the electrolysiscell.
 31. Apparatus as claimed in claim 20, which includes a separatordevice for separating the gas which is to be generated from the liquid.32. Apparatus as claimed in claim 30, in which the separator deviceincludes a separator chamber having a liquid outlet through which liquidis discharged to the second chamber, and a gas outlet, the gas outlethaving a valve which closes when the liquid level in the separatorchamber exceeds a predetermined level.
 33. Apparatus as claimed in claim30, in which the separator device includes a quantity of an adsorbent34. Apparatus as claimed in claim 30, in which the housing includesformations for fixing the separator device to the housing.
 35. Apparatusas claimed in claim 20, in which the housing is formed at least partlyfrom a polymeric material.
 36. Apparatus as claimed in claim 34, inwhich the first and second chambers are formed from the same polymericmaterial.
 37. Apparatus as claimed in claim 34, in which the first andsecond chambers are formed together in a molding operation. 38.Apparatus as claimed in claim 20, in which a portion of the wall of thehousing which defines the first chamber is defined by a line of weaknessso that the wall fails at the line of weakness when the pressure in thefirst chamber reaches an excessively high level.
 39. Apparatus asclaimed in claim 20, in which the first chamber, second chamber and thefirst channel are formed as separate pieces which are assembled togetherto form the housing as a single component.
 40. Apparatus as claimed inclaim 20, in which the first chamber, second chamber and the firstchannel are formed as a single piece.
 41. Apparatus as claimed in claim20, in which the walls of the first and second chambers are formed fromthe same material.